When the alarm goes worldwide that an embassy or consulate is being attacked, the entire U.S. military swings into rescue mode, without waiting for any orders from the White House. The military does all of the operational planning and begins to execute the rescue op.
The one thing they CAN'T do is cross an international border without permission from POTUS. So the US Military will be inbound full-steam-ahead to make the rescue, and all they need from POTUS is a "proceed" order. In this case, they got a "stand down" instead.
This is at the POTUS level, it is not a decision taken at State. State and the military (JCS) should be in the Situation Room with POTUS soon after a critical incident like this begins, so all decisions can be made in real time. (I have heard nowhere that POTUS went into the Situation Room. Oval office briefly, but not down to the Situation Room, where the "war planning" screens and commo tools are all located.)
But if POTUS punts after the brief Oval Office meeting with Dempsey and Hillary and goes upstairs to the family quarters....the stranded Americans will die.
Only POTUS can give the order to cross international borders. Only POTUS can allow US warplanes to give air support to Americans battling on the ground in a foreign country. If POTUS makes himself unavailable, the Americans will die.
Even the VEEP or Sec State cannot make that call. The VEEP can only do it if the POTUS is determined to be medically unable to perform his functions. If the POTUS goes upstairs and turns off his phone, there is nothing anybody can do about it. Nothing.
